Reliability-based Failure Probability and Resistance Factor for Flush-Drilled Anchors in Taipei Basin

The goal of this research is to calibrate the reliability-based resistance factor (= reciprocal of safety factor) of flush drilled soil anchors for their ultimate pullout capacities based on in-situ anchor pullout test data in the alluvial soils of Taipei basin. Efforts are taken to quantify the uncertainties with a full probabilistic analysis approach. The resistance factor is calibrated using the in-situ test results of 46 anchors with a rigorous theoretical approach which constructs the relationship between the resistance factor and failure probability. With this relationship, the reliability corresponding to the code regulation can be verified. From the results of the analysis, it is found that the borehole enlargement due to the flush drilling is quite significant. In other words, the actual diameter of the fixed anchor end may be much larger than the nominal diameter of the drilling casing. Consequently, the safety factor of three which is recommended by most anchor codes for the working anchor pullout capacity is found to be too conservative. The results of this study should be of value for the reliability-based design of flush drilled soil anchors in alluvial soils.

• Introduction

• Database

• Models for pullout capacity

• Modeling of uncertainties

• Calibration of resistance factor

• Results of stochastic simulations

• Conclusion

• References